Will Exhaust Pipe drip water?

[jeclarke]

I’m about to have a Big Dawg natural gas heater installed in my 3 car garage. The best placement means that the exhaust pipe will need to run from the back of the garage to the front, above 1 of my cars. This will be a 21’ horizontal pipe. I will only use the heater occasionally when I’m going to be working on my car. I live in PA.

Is the exhaust pipe going to be wet on the outside (condensation) and drip on my car or whatever is below it?

 

[larry_g]

Not if you wrap it with a pipe insulating material..
lg
no neat sig line

 

[theoldwizard1]

H2O is a common by product of most fossil fuel combustion. It is usually vapor by the time it hits the air.

 

[rlitman]

The only potential for a vent pipe dripping is when it's run wrong. Insulation isn't the answer either.

The vent pipe will be above room temperature, so condensation will not form on the outside when the heat is running. That's not an issue.

The issue is that the combustion exhaust is very humid, and there is the potential for condensation to form inside the pipe. There are several ways to combat this. You run the pipe in a way that there are no low points that can trap condensation, and you setup the system so that the exhaust temperature keeps everything above the dew point.

Anyway, this is all spelled out in the instructions.

 

[Showkey]

CATIII is sealed and not likely drip water inside.
Heater exhaust will drip water, about a gallon of water for every “gallon” of fuel burned. The exhaust water and vapor is acidic........so dripping on car should be avoided.

CATIII can easily be over $1 per inch length plus termination fitting plus install costs so 21’ is far from ideal ?

Instructions notes bullet points like:

1.runs as short as possible with a minimum number of elbows.
2. Do not terminate vent directly below roof eaves or above a walk- way, or any other area where condensate dripping may be trouble- some and may cause some staining. Avoid windows where steam may cause fogging or ice buildup.

 

[larry_g]

The only potential for a vent pipe dripping is when it's run wrong. Insulation isn't the answer either.

I disagree. The vent pipe is open to the outside air and if cold air fills the pipe and cools it the warm moist air inside the building will condense on it.

I do agree that the exhausting of combustion byproducts will not cause problems on the outside of the pipe.

lg

 

[The Cobbler]

are you sure the heater is rated to run 20' horizontal flue?

 

[Showkey]

are you sure the heater is rated to run 20' horizontal flue?

Agree it could be border line. The exhaust will condensing by the end. B vent in this application would be a real problem. Yes it’s not rated or allowed in horizontal but it’s still being used.
Distance Varies with manufacturer.
Most are 25-30’ max straight line less for each 90* elbow.

 

[jeclarke]

Thanks for all the responses. I wasn’t familiar with CATIII pipe. It is expensive! My best option then is for a short exhaust pipe but thru the front of the house. I really don’t think I like the way this will look.

Any suggestions how to make the exhaust not so ugly?

Also the pipe would be under an eve with vent holes that leads to the attic. Any suggestions how to block the holes and how far to each side of the exhaust pipe I would need to do this?

 

[Showkey]

Move the entire heater to the back wall. Might mean longer gas line, power or other costs, but a better solution.

Exhaust out the front of the building is an aesthetic mistake which will questioned for years to come.

Another solution would be Rinnai heater wall mount vented in the side wall. They are more expensive units but the venting is small opening and short.

 

[k-os]

Thanks for all the responses. I wasn’t familiar with CATIII pipe. It is expensive! My best option then is for a short exhaust pipe but thru the front of the house. I really don’t think I like the way this will look.

Any suggestions how to make the exhaust not so ugly?

Also the pipe would be under an eve with vent holes that leads to the attic. Any suggestions how to block the holes and how far to each side of the exhaust pipe I would need to do this?

The minimum offsets from eaves, windows, etc should be spelled out in the manual for your heater. Typically the exhaust will need to extend out some minimum amount from your eaves.